Royal surrendering rule like in Richard III? (4)

I believe the answer is:

egal

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'iii?' is the definition.
Both the answer and definition are adjectives.
Maybe you can see a link between them that I don't see?

I don't understand the rest of the clue.

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(Other definitions for egal that I've seen before include "Of the same value to Shakespearean" , "fit" .)

I've seen this clue in The Sunday Times and The Times.

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